Belt tightener

The utility model discloses a belt tightener installed on an accessory bracket to tighten a belt. The belt tightener comprises a frame body with a first via hole, a tightening wheel connected with the frame body through a bearing, a base with a second via hole, and a step shaft sleeve with a main section and an auxiliary section. The main section is threaded in the first via hole. The auxiliary section is threaded in the second via hole by way of interference fit. The step ring surface of the shaft sleeve leans against the top face of the base. The bottom face of the base leans against the accessory bracket. A gap is arranged between the tail end face of the shaft sleeve toward the accessory bracket and the accessory bracket. A gap is reserved between the end face of the shaft sleeve and an accessory installation bracket in the belt tightener to ensure the contact area of the base of the tightener and the accessory instillation bracket, disperse the alternate shear stress borne by a fixed bolt in the diameter